We currently have an active protocol for preclinical pharmacokinetic analysis of new agents. Over the past year, we have further developed a close working relationship with the Pharmacology and Experimental Therapeutics Section of the POB to partner in pharmacologic investigations of new agents. We have successfully obtained new agents from intramural and extramural sources to investigate, and are developing biomarkers in the preclinical setting. In general, for an antitumor agent to have an effect, you need: -an active agent, -Delivered to tumor -Present at tumor site in its active form -Effective concentrations -Long enough period of time -Tolerability at doses necessary to achieve above -For targeted therapy, need to know if the target is present We are developing methods to further investigate the mechanisms of action of agents currently in clinical trials, and investigate biomarkers or surrogate markers of drug activity and tumor response. We are developing a new animal model for brain microdialysis.